Bilirubin, a water-insoluble tetrapyrrole, is an orange-yellow pigment produced from the heme. It can poison many vital cell functions of the human body but the liver clears it from the blood by conjugating it to a water-soluble form and excretes it into the bile. However, some newborns, due to their incomplete maturation of the several steps involved in the bilirubin metabolism and excretion, have bilirubin concentrations in their blood which are much greater than the normal upper limits, thereby leading to jaundice in severe cases. Severely jaundiced babies can suffer from mental retardation, deafness, seizures and death. In children and adults, disorders of the liver can also lead to the accumulation of bilirubin to toxic levels in the body.
These concerns are the basis for research into finding suitable controls for bilirubin toxicity. So far, there are two commonly used approaches for severely jaundiced patients: phototherapy and exchange transfusion. However, both techniques present severe drawbacks and limitations.
Phototherapy is inadequate for the treatment of severe cases of jaundice since only 15% of the total bilirubin can be photoisomerized through the skin. Furthermore, phototherapy induces DNA damage and causes depletion of riboflavin, tryptophan and histidine in cultured mammalian cells.
In severe cases of jaundice, patients can undergo blood exchange transfusion. However, the mortality of a single exchange transfusion approaches 1% and some patients must undergo more than one exchange. Problems such as hypoglycemia, acidosis, coagulopathies as well as chances of transmitting viral infections such as hepatitis and AIDS to the patients are also common risks inherent to this approach.
In order to avoid problems associated with exchange transfusions, various efforts have been made to develop resins for removal of bilirubin from the blood by adsorption through chromatography. Generally, the selectivity of this technique is poor and consequently several other blood components including essential compounds such as thyroxine, cortisol and aldosterone are also removed from the blood stream.
Recently, bilirubin oxidase has been suggested as a treatment approach. However, this enzyme is expensive and not readily available.
Therefore, an inexpensive, easily accessible method for the removal of bilirubin from blood would be highly desirable.